The present invention relates to a device for reproducing data from a CD-ROM or like storage medium.
As is disclosed in Japanese Laid-Open Patent No. Hei 10-83615, for example, data is generally read out by first measuring vibration value by rotating a disc at a maximum speed prior to reproducing data and, when the vibration value is beyond a predetermined threshold level, by rotating the disc at a speed lower than the maximum speed. A CD-ROM is a CD (compact disc) used as a ROM (read-only memory) and is used in computer systems just like a semiconductor ROM. As high speed processing is required in computer systems, rotational speed of a CD-ROM is generally set at a speed several to several tens of times higher than the rotational speed (200 rpm) of audio CD""s.
When a CD-ROM is scanned by a disc reproducer at such a high speed as 40 times the standard scanning speed, for example, an error of a tracking control system for correcting eccentricity of track due to disc vibration increases thus resulting in an error in reading-out data on the disc and requiring a retrial thereby lowering performance of reproduction. Also, when a low-quality disc having a large mass eccentricity is rotated, not only the disc but also the entire disc reproducer vibrates, and the vibration affects a hard disc drive (HDD) installed in a housing of a computer system together with the disc reproducer. There is thus a possibility of causing read/write error in the HDD, which lowers reliability of the entire computer system. Also, even if an error may not be generated in reading/writing of the HDD, vibration of the disc reproducer gives an unpleasant feeling to a user. The above problem can be solved by either reducing mass eccentricity of the CD-ROM or lowering the rotational speed. However, in practice, there is a large dispersion in the quality of CD-ROM""s and some discs are inappropriate for reproduction at a high speed.
In order to solve this problem, vibration value of a disc reproducer is detected and, when the detected value is beyond a preset threshold level, the reproducer is operated at a reduced disc rotational speed. However, as the detected vibration value varies due to manufacturing dispersion of individual disc reproducers, in a conventional fixed threshold level design, there has been a problem of inability to precisely switching the disc rotational speed.
It is an object of the present invention to provide a disc reproduction method and device that can stably reproduce data at as high speed as possible for both a high-quality storage medium disc and low-quality storage medium disc. Also, the present invention employs a method of detecting the maximum data reproducible speed by performing vibration detection from the side of a lower disc speed in order not to give an unpleasant feeling to a user by generating large vibration even during a vibration detecting mode.
In order to achieve the above object, the data reproducer in accordance with the present invention comprises the following: namely, disc rotating means structured in a manner such that a storage medium disc having data recorded on a spiral or concentric track and a center hole can be detachably fit to a spindle of the reproducer, a signal converter for reading out the data from the disc, and moving means for moving the signal converter in the radial direction of the disc.
Next, an allowable-limit vibration value is set in an adjusting process of individual data reproducer manufacture, and a plurality of allowable-limit mass eccentricity discs (hereinafter referred to as xe2x80x9cstandard vibrating discsxe2x80x9d) with a known mass eccentricity is prepared of which the vibration values at the maximum data reproduction speed and lower data reproduction speeds are equivalent to the allowable-limit vibration value. Each of the discs is then mounted and the difference (Pxe2x80x94P value) between the peak value in the positive direction of a tracking servo error signal (TE signal) and the peak value in the negative direction as obtained by rotating at a predetermined reproduction speed is detected as the vibration value of the disc reproducer in question, and the vibration value is set as the threshold level for the combination of the data reproduction speed and the vibration-limit disc as described later. When a disc with an unknown mass eccentricity is mounted, vibration value is detected at a data reproduction speed on the lower speed side that is lower than the maximum reproduction speed (hereinafter simply referred to as xe2x80x9cthe low speed sidexe2x80x9d, the opposite side being referred to as xe2x80x9cthe high speed sidexe2x80x9d), followed by a first step of measuring a voltage (hereinafter referred to as xe2x80x9cvibration valuexe2x80x9d) proportional to the disc vibration that is occurring and a second step of judging whether or not the vibration value is below the threshold level. When it is judged in the second step that the vibration value is below the threshold level, the disc is rotated at the above-mentioned reproduction speed by the disc rotating means, and the signal converter reads out the data from the disc. When it is judged that the mass eccentricity is not within the allowable range, the disc is rotated by the disc rotating means at a data reproduction speed lower than the vibration detecting speed so that the afore-mentioned data can be read out from the disc with the signal converter.
In other words, a plurality of vibration detecting speeds (which may be the same as the data reproduction speed) is set at the maximum data reproduction speed and at speeds lower than that, and an allowable-limit mass eccentricity disc (standard vibrating disc) is prepared for each of the detecting speeds. The first threshold level for the first vibration detecting speed is set at the vibration value as detected on an allowable-limit mass eccentricity disc Da at a first vibration detecting speed. When a disc D with an unknown mass eccentricity is mounted, if the detected vibration data at the first vibration detecting speed is within the range of the first threshold level, vibration detection is carried out at a second vibration detecting speed that is higher than the first vibration detecting speed.
The second threshold level for the second detection speed is set at the vibration data as detected on an allowable-limit vibrating disc Db at a second speed. When the detected vibration data at the second vibration detecting speed of the disc D with an unknown mass eccentricity is within the range of the second threshold level, vibration detection at a third vibration detecting speed is carried out. In this way, vibration detection is carried out in sequence from the low-speed side toward the high-speed side. At the stage a detected vibration data is found to be outside of respective threshold level range, the data is read out with a vibration detecting speed lower than the vibration detecting speed at which the detected vibration value was outside of respective threshold level range as the maximum speed. A data reproducer having such data reading means is hereby proposed.
According to a reproducer having the above structure, an allowable mass eccentricity of a disc is precisely set as a threshold level (allowable range) for each individual disc reproducer at the time the disc is reproduced at the maximum rotational speed at which data is reproducible. Consequently, by changing the maximum speed at which data can be reproduced depending on the mass eccentricity, it becomes possible to carry out high-speed reproduction of a disc that has a small mass eccentricity at the maximum speed available with the data reproducer, and to carry out reproduction of a disc having a large mass eccentricity under a condition in which a problem associated with mass eccentricity will not occur.
Also, according to the present invention, as high-speed rotation of a low-quality disc can be prevented, vibration value of a disc or data reproducer is limited. As a result, ripple effect of vibration on a separate device (HDD, for example) contained in the same housing as that of a data reproducer according to the present invention can be limited, thus enabling normal operation of the separate device (HDD, for example). Also, as vibration of the disc or data reproducer is limited, unpleasant feeling to a user will be reduced.
Furthermore, in the present invention, as the maximum reproduction speed that is available within the allowable limit of the vibration value is determined by carrying out vibration detection two or more times from the low speed side of the disc rotation toward the high speed side, unpleasant feeling to the user can be prevented in the vibration detecting mode, too.